JPH06110931A - Duplex data base device - Google Patents

Abstract

PURPOSE:To provide a duplex data base device in which the load of a data transmission processing can be reduced. CONSTITUTION:An error detection code in a data base DB1 in an activating state is preliminarily compared with the error detection code in a data base DB2 in a waiting state before a copy is periodically operated. A communication controller C1 reads the data from an error detection code storage device F1, and transmits the data through a transmission path 10 to a communication controller C2. And also, the communication controller C2 transmits the data through a transmission path 12 to an error detection code collating device G2. Then, the error detection code collating device G2 receives the data from the transmission path 12, reads the corresponding data through a transmission path k2 from an error detection code storage device F2, and compares the data with the data transmitted from the communication controller C2. Then, when the data are not matched, the copy of the data is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplex database system suitable for use in a switchboard, a computer, etc. having a database.

[0002]

2. Description of the Related Art A conventional dual database system is shown in FIG.
As shown in FIG. 3, the database DB1 is in an operating state and the database DB2 is in a standby state. Data is exchanged with an external device via a database access transmission line i, and storage between the databases DB1 and DB2 is performed. The copying of the contents is performed via the transmission line 20. Each database includes a database control device A, a data storage device B, a communication control device C, an error detection code generation device D, a storage error detection device E, an error detection code storage device F, a database control device A and a data storage device B. A transmission line a that connects the data storage device B and the communication control device C, a transmission line c that connects the data storage device B and the error detection code generation device D, an error detection code generation device D, and a storage error detection device. It comprises a transmission line d connecting E and a transmission line e connecting the error detection code generator D and the error detection code storage device F, and a transmission line f connecting the storage error detection device E and the error detection code storage device F. There is.

In such a configuration, the writing of data in the duplicated database device is performed by writing to both the operating state database DB1 and the standby state database DB2 through the transmission line i. For reading data from the redundant database device, the database DB1 in the operating state is normally used, and when a failure occurs in this, the database DB2 in the standby state is immediately placed in the operating state and used. Therefore, the database DB
The data storage device B1 in 1 and the data storage device B2 in the database DB2 must always maintain the same storage state.

Therefore, in the conventional dual database device, the data storage device B in the database DB1 which is in the operating state is periodically sent via the transmission line 20.
All the data of No. 1 were compared with the corresponding data of the data storage device B2 in the database DB2 in the standby state. In this case, the operating state database D
The data stored in the data storage device B1 in B1 is read by the communication control device C1, and this is transmitted to the communication control device C2 in the standby database DB2 via the transmission path 20. It was compared by C2 with the contents of data store B2.

As a result of the comparison, if the storage contents of the data storage device B1 and the data storage device B2 differ, the storage contents of the data storage device B2 were rewritten to the storage contents of the data storage device B1.

When data is written in the data storage devices B1 and B2, the error detection code generation device D is always used.
1 and D2 generate an error detection code from the write data, and this is written in the error detection code storage devices F1 and F2. Further, when data is read from the data storage devices B1 and B2, error detection codes are generated from the read data by the error detection code generation devices D1 and D2, which is already the error detection code storage device F1.
The error detection code corresponding to the read data stored in F2 was compared with the storage error detection devices E1 and E2 to check whether there was a storage error. Further, the error detection code storage devices F1 and F2 have not been used for purposes other than storage error detection.

[0007]

By the way, in the prior art,
Regardless of whether the database DB1 in the operating state is updated or not, the database DB2 in the standby state is updated by periodically comparing all the data in the data storage device B1 with the data storage device B2 in the standby state. It was. For this reason, since the processing load related to data transfer becomes very large, the transmission line 20 needs to be of the parallel line type, and the complexity of the wiring work caused by these is due to the operating state database DB1 and the standby state database. There has been a problem that the degree of freedom of the relative arrangement form of DB2 is greatly limited.

The present invention has been made in view of the above-mentioned problems, and provides a dual database apparatus capable of reducing the load of data transmission processing when copying the storage contents of one database to the other database. The purpose is to do.

[0009]

In order to solve the above problems, in the invention described in claim 1, a data storage device, a database control device, an error detection code generation device, and an error detection code storage device. In a dual database device configured by a plurality of database devices having a device, a storage error detection device, and a communication control device, an error detection code collating device is provided, and when a plurality of database devices are interconnected, The error detecting codes are compared by the error detecting code collating device.

According to the invention described in claim 2,
The storage area of the data storage device is divided into blocks, and the storage area is read and written in block units.

[0011]

According to the invention described in claim 1, before copying the data stored in one data storage device to the other data storage device, the error detection code in one database and the other database The error detection code in the above is compared, and the data is copied only when there is a difference between the two.

According to the second aspect of the present invention, the error detection code in one database and the error detection code in the other database are periodically arranged in a cycle according to the data rewriting frequency for each block. Only when there is a difference between the two, the other database is updated by rewriting only the relevant area of the other data storage device.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing the configuration of this embodiment. In this figure, the difference from FIG. 2 is that in the database DB, the error detection code collating device G,
The error detection code collating device G and the error detection code storage device F
A transmission line k that connects the error detection code collating device G and the communication control device C, a transmission line j that connects the communication control device C and the error detection code storage device F, and a transmission line 10. It is a form. Hereinafter, these will be mainly described.

First, in the database according to this embodiment, an error in the operating database DB1 is previously made before the storage contents of the operating database DB1 are periodically copied to the standby database DB2. The data stored in the detection code storage device F1 is compared with the corresponding data stored in the error detection code storage device F2 in the standby database DB2. At this time, the communication control device C1 reads the data from the error detection code storage device F1 and transmits it to the communication control device C2 via the transmission path 10. Further, the communication control device C2 transmits to the error detecting code collating device G2 via the transmission line l2. And
The error detection code collating device G2 receives the data from the transmission line 12 and reads out the corresponding data from the error detection code storage device F2 via the transmission line k2 and the data sent from the communication control device C2. Make a comparison.

Here, the data stored in the error detection code storage device F1 in the operating state database DB1 is compared with the corresponding data stored in the error detection code storage device F2 in the standby state database DB2. Since it is premised that the stored contents are identical when collating, considering that data may always be written from the external device to the duplicated database device, the error detection code storage devices F1 and F2 are stored. In the area where the stored data has not been rewritten, the data is read from the corresponding areas in synchronization with the timing. Timing synchronization and detection of an area in which the stored data in the error detection code storage devices F1 and F2 are not rewritten can be easily realized by using an external timing generation circuit or communication control devices C1 and C2. .

Further, in this embodiment, when the communication control device C accesses the data in the data storage device B, the communication control device C handles the data storage device B in blocks so that the data storage device B is handled and rewritten. The database DB1 in the active state is in the standby state by periodically comparing the error detection codes of the blocks with high frequency with a short cycle and periodically comparing the error detection codes of the blocks with a low rewriting frequency with the long cycle. It is possible to further reduce the processing load when copying to the database DB2.

If no difference is detected as a result of collating the data, the operating state database D
The data stored in the data storage device B1 in B1 is considered to be the same as the data stored in the data storage device B2 in the database DB2 in the standby state,
The operation of copying the data stored in the data storage device B1 to the data storage device B2 is not performed.

On the other hand, when a difference is detected as a result of collating the data, the database DB in the standby state
It is considered that the data stored in the data storage device B2 in 2 is erroneous, and the work of copying the data stored in the data storage device B1 to the data storage device B2 is performed. This data copying operation is performed according to the conventional method.

According to this embodiment, before copying the data in the data storage device, the data stored in the error detection code storage device are compared with each other. If there is no difference, the data is not copied, and the difference is obtained. Since the data is copied only after that, the load of the data transmission processing at the time of copying can be reduced. Further, at this time, since the amount of signals exchanged for comparison / collation decreases, even if a serial type line is used as a transmission line connecting the databases DB1 and DB2, work efficiency does not decrease.

[0020]

According to the invention described above, before the data stored in one data storage device is copied to the other data storage device, the error detection code in one database and the error detection code in the other database are copied. The error detection code is compared, and the data is copied only when there is a difference between them, and the data is not copied if there is no difference between the two, so the load of the data transmission processing is reduced during copying. It is possible (Claim 1). Further, since the detection codes are collated periodically for each block in a cycle according to the data rewriting frequency, the load of the data transmission processing can be further reduced (claim 2). Therefore, it is possible to reduce the processing load when updating the database, which makes it possible to use a serial type line, which has a small capacity as compared to a parallel type line, but is flexible in wiring work, as a transmission line. Therefore, there is an advantage that it is possible to increase the degree of freedom of the relative arrangement form between the databases.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional duplex database.

[Explanation of symbols]

10 ... Transmission path, DB ... Database, A ... Database control device, B ... Data storage device, C ... Communication control device, D ... Detection code generation device, E ... Storage error detection device, F ... ... detection code storage device, G ... error detection code collation device

Claims (2)

[Claims] 1. A plurality of database devices including a data storage device, a database control device, an error detection code generation device, an error detection code storage device, a storage error detection device, and a communication control device. A duplicate database device, wherein an error detection code collating device is provided, and when a plurality of database devices are mutually connected, the error detecting codes are compared by the error detecting code collating device. 2. The dual database apparatus according to claim 1, wherein the storage area of the data storage device is divided into blocks, and the storage area is read and written in block units.